No, it does not have any special meaning in Czech…

Actually avast has its own meaning in english - here is the quote from Merriam-Webster dictionary:
avast – a nautical command to stop or cease
Etymology: perhaps from Dutch houd vast hold fast
Date: 1681

Pavel

So although avast! stops viruses, it is also widely used by pirates (and their parrots) all over the world :smiley: